Saturn: Lord of the Rings, Now King of the Moons!

It seems Saturn is the current winner of the Moon Race with Jupiter. Like a Baseball Home Run derby, Saturn has now surpassed Jupiter with a surplus of three more moons, having 82 against Jupiter’s 79. Barry Bonds and Mark McGuire would envy such totals.

These twenty newly discovered moons are not your typical moons like our natural satellite, the Moon. Saturn, like Jupiter, has a smorgasbord of moons divided into several groups. Seventeen of these new moons are irregular moons because their orbits are retrograde and are classified in the “Norse group” of Saturnian satellites. The other three newly discovered moons have a prograde orbit with a period of three Earth years or more to circle Saturn. (https://www.space.com/saturn-20-newfound-moons-naming-contest.html ) This is not typical of prograde moons to be so far from a planet.

Prograde orbiting moons are innately inclined to follow close to the orbital plane of the primary planet. They would have formed naturally in a close orbit around their primary; whereas retrograde or irregular moons orbit “backwards” and are typically small, heavily inclined in their orbit, and usually spaced far out from the primary planet.

Scott Sheppard led the discovery team which includes his colleagues, David Jewitt of the University of California, Los Angeles, and Jan Kleyna of the University of Hawaii. They found the 20 new Saturn moons using the Subaru Telescope in Hawaii (https://subarutelescope.org/). Sheppard is no stranger to the outer realm of the Solar System.  In the past two decades he has found numerous moons, comets, and minor planets in his distinguished astronomical career. (https://en.wikipedia.org/wiki/Scott_S._Sheppard )

The Saturn satellite system is divided into several moon groups such as large moons, ring moonlets, shepherd moons, co-orbital and irregular moons, with the latter being further divided into three sub-groups.  (https://en.wikipedia.org/wiki/Moons_of_Saturn#Irregular_moons ) These sub-groups are divided as and are so named: Inuit, Gallic, and Nordic (or Phoebe) groups, Phoebe being the largest of the irregular moons, but still small itself, so these new moons are not very impressive in size, averaging 3 miles in diameter.

If I were to arrive at Saturn in a spaceship like the Millennium Falcon with the Star Wars film legendary Jedi Master, Obi-Wan Kenobi, I’m sure if he spotted those newly discovered “moons” that he would certainly exclaim, “That’s no moon(s)!” — though perhaps that response is more relevant to Saturn’s own Death Star-looking moon, Mimas.

This discovery leads me to wonder what is the lower limit to a so-called “moon,” the question, how small can a “moon” be? How many more of these “tiny” satellites are to be discovered around the gas giant planets? Is the Moon Race over? And which planet will be the first to have a hundred moons?

 


 

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